Pipe and other tubulars, terms used interchangeably herein, have been lined with polymeric liners (e.g., polyethylene, nylon 11, etc.) for many years and several installation techniques are known to the art. These systems have been used principally in offshore and onshore pipelines, and in downhole production tubulars. Their scope has generally been limited to corrosion and erosion protection. However, they have also been used in monitoring for integrity of the composite liner-host system, as disclosed for example in U.S. Pat. No. 5,072,622 (Roach and Whitehead).
Generally, the liner 11 resides in close-tolerance with the host pipe 10 along its length, forming a stable composite system (as shown in FIG. 1, which is a cutaway end view of a lined tubular). The installed liner may be either of a loose-fit or a compressed-fit variety, both well known to the art. In all but very low pressure applications, the stresses induced by fluid pressure from within the liner are transmitted to the surrounding, xe2x80x98hostxe2x80x99 tubular, and are resisted by the host tubular. The liner acts as an intermediary layer.
The invention described herein expands the range of possible applications for such liners through controlled manipulation of annular fluids within the lined tubular systems. The disclosed embodiments of the invention provide, among other features, a continuous annulus along the length of plastic-lined tubular, and if applicable, through any intermediary joints, and manipulation of fluids within the annulus.
The present invention may be applied to virtually all types of lined tubular systems, including but not limited to pipelines, intra-facility piping networks, and well tubulars.
A first aspect of the invention relates to structures and methods for forming a fluid-carrying annulus between the internal liner of a host tubular and the inner surface of a host tubular itself.
A second aspect of the invention provides methods and structures for improved fluid circulation within the annulus. Fluid circulation may be employed for measurement of fluid flow, for heat transfer within the pipeline, for treatment or removal of undesired or detrimental fluids, or for combinations of these features.
A third aspect of the invention provides methods and structures for reducing the propensity for propagation of cracks in a host tubular.
Other features and advantages of the invention will become apparent from the following description of embodiments of the invention which refers to the accompanying drawings.